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Date: Tue, 4 May 2010 01:48:23 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: David L Stevens <dlstevens@...ibm.com>
Cc: netdev@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.osdl.org
Subject: Re: [PATCHv7] add mergeable buffers support to vhost_net
On Wed, Apr 28, 2010 at 01:57:12PM -0700, David L Stevens wrote:
> This patch adds mergeable receive buffer support to vhost_net.
>
> Signed-off-by: David L Stevens <dlstevens@...ibm.com>
>
> diff -ruNp net-next-v0/drivers/vhost/net.c net-next-v7/drivers/vhost/net.c
> --- net-next-v0/drivers/vhost/net.c 2010-04-24 21:36:54.000000000 -0700
> +++ net-next-v7/drivers/vhost/net.c 2010-04-28 12:26:18.000000000 -0700
> @@ -74,6 +74,23 @@ static int move_iovec_hdr(struct iovec *
> }
> return seg;
> }
> +/* Copy iovec entries for len bytes from iovec. Return segments used. */
> +static int copy_iovec_hdr(const struct iovec *from, struct iovec *to,
> + size_t len, int iovcount)
> +{
> + int seg = 0;
> + size_t size;
> + while (len && seg < iovcount) {
> + size = min(from->iov_len, len);
> + to->iov_base = from->iov_base;
> + to->iov_len = size;
> + len -= size;
> + ++from;
> + ++to;
> + ++seg;
> + }
> + return seg;
> +}
>
> /* Caller must have TX VQ lock */
> static void tx_poll_stop(struct vhost_net *net)
> @@ -109,7 +126,7 @@ static void handle_tx(struct vhost_net *
> };
> size_t len, total_len = 0;
> int err, wmem;
> - size_t hdr_size;
> + size_t vhost_hlen;
> struct socket *sock = rcu_dereference(vq->private_data);
> if (!sock)
> return;
> @@ -128,13 +145,13 @@ static void handle_tx(struct vhost_net *
>
> if (wmem < sock->sk->sk_sndbuf / 2)
> tx_poll_stop(net);
> - hdr_size = vq->hdr_size;
> + vhost_hlen = vq->vhost_hlen;
>
> for (;;) {
> - head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
> - ARRAY_SIZE(vq->iov),
> - &out, &in,
> - NULL, NULL);
> + head = vhost_get_desc(&net->dev, vq, vq->iov,
> + ARRAY_SIZE(vq->iov),
> + &out, &in,
> + NULL, NULL);
> /* Nothing new? Wait for eventfd to tell us they refilled. */
> if (head == vq->num) {
> wmem = atomic_read(&sock->sk->sk_wmem_alloc);
> @@ -155,20 +172,20 @@ static void handle_tx(struct vhost_net *
> break;
> }
> /* Skip header. TODO: support TSO. */
> - s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
> + s = move_iovec_hdr(vq->iov, vq->hdr, vhost_hlen, out);
> msg.msg_iovlen = out;
> len = iov_length(vq->iov, out);
> /* Sanity check */
> if (!len) {
> vq_err(vq, "Unexpected header len for TX: "
> "%zd expected %zd\n",
> - iov_length(vq->hdr, s), hdr_size);
> + iov_length(vq->hdr, s), vhost_hlen);
> break;
> }
> /* TODO: Check specific error and bomb out unless ENOBUFS? */
> err = sock->ops->sendmsg(NULL, sock, &msg, len);
> if (unlikely(err < 0)) {
> - vhost_discard_vq_desc(vq);
> + vhost_discard_desc(vq, 1);
> tx_poll_start(net, sock);
> break;
> }
> @@ -187,12 +204,25 @@ static void handle_tx(struct vhost_net *
> unuse_mm(net->dev.mm);
> }
>
> +static int vhost_head_len(struct vhost_virtqueue *vq, struct sock *sk)
> +{
> + struct sk_buff *head;
> + int len = 0;
> +
> + lock_sock(sk);
> + head = skb_peek(&sk->sk_receive_queue);
> + if (head)
> + len = head->len + vq->sock_hlen;
> + release_sock(sk);
> + return len;
> +}
> +
> /* Expects to be always run from workqueue - which acts as
> * read-size critical section for our kind of RCU. */
> static void handle_rx(struct vhost_net *net)
> {
> struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
> - unsigned head, out, in, log, s;
> + unsigned in, log, s;
> struct vhost_log *vq_log;
> struct msghdr msg = {
> .msg_name = NULL,
> @@ -203,14 +233,14 @@ static void handle_rx(struct vhost_net *
> .msg_flags = MSG_DONTWAIT,
> };
>
> - struct virtio_net_hdr hdr = {
> - .flags = 0,
> - .gso_type = VIRTIO_NET_HDR_GSO_NONE
> + struct virtio_net_hdr_mrg_rxbuf hdr = {
> + .hdr.flags = 0,
> + .hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE
> };
>
> size_t len, total_len = 0;
> - int err;
> - size_t hdr_size;
> + int err, headcount, datalen;
> + size_t vhost_hlen;
> struct socket *sock = rcu_dereference(vq->private_data);
> if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
> return;
> @@ -218,18 +248,19 @@ static void handle_rx(struct vhost_net *
> use_mm(net->dev.mm);
> mutex_lock(&vq->mutex);
> vhost_disable_notify(vq);
> - hdr_size = vq->hdr_size;
> + vhost_hlen = vq->vhost_hlen;
>
> vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
> vq->log : NULL;
>
> - for (;;) {
> - head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
> - ARRAY_SIZE(vq->iov),
> - &out, &in,
> - vq_log, &log);
> + while ((datalen = vhost_head_len(vq, sock->sk))) {
> + headcount = vhost_get_desc_n(vq, vq->heads,
> + datalen + vhost_hlen,
> + &in, vq_log, &log);
> + if (headcount < 0)
> + break;
> /* OK, now we need to know about added descriptors. */
> - if (head == vq->num) {
> + if (!headcount) {
> if (unlikely(vhost_enable_notify(vq))) {
> /* They have slipped one in as we were
> * doing that: check again. */
> @@ -241,46 +272,53 @@ static void handle_rx(struct vhost_net *
> break;
> }
> /* We don't need to be notified again. */
> - if (out) {
> - vq_err(vq, "Unexpected descriptor format for RX: "
> - "out %d, int %d\n",
> - out, in);
> - break;
> - }
> - /* Skip header. TODO: support TSO/mergeable rx buffers. */
> - s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
> + if (vhost_hlen)
> + /* Skip header. TODO: support TSO. */
> + s = move_iovec_hdr(vq->iov, vq->hdr, vhost_hlen, in);
> + else
> + s = copy_iovec_hdr(vq->iov, vq->hdr, vq->sock_hlen, in);
> msg.msg_iovlen = in;
> len = iov_length(vq->iov, in);
> /* Sanity check */
> if (!len) {
> vq_err(vq, "Unexpected header len for RX: "
> "%zd expected %zd\n",
> - iov_length(vq->hdr, s), hdr_size);
> + iov_length(vq->hdr, s), vhost_hlen);
> break;
> }
> err = sock->ops->recvmsg(NULL, sock, &msg,
> len, MSG_DONTWAIT | MSG_TRUNC);
> /* TODO: Check specific error and bomb out unless EAGAIN? */
> if (err < 0) {
> - vhost_discard_vq_desc(vq);
> + vhost_discard_desc(vq, headcount);
> break;
> }
> - /* TODO: Should check and handle checksum. */
> - if (err > len) {
> - pr_err("Discarded truncated rx packet: "
> - " len %d > %zd\n", err, len);
> - vhost_discard_vq_desc(vq);
> + if (err != datalen) {
> + pr_err("Discarded rx packet: "
> + " len %d, expected %zd\n", err, datalen);
> + vhost_discard_desc(vq, headcount);
> continue;
> }
> len = err;
> - err = memcpy_toiovec(vq->hdr, (unsigned char *)&hdr, hdr_size);
> - if (err) {
> - vq_err(vq, "Unable to write vnet_hdr at addr %p: %d\n",
> - vq->iov->iov_base, err);
> + if (vhost_hlen &&
> + memcpy_toiovecend(vq->hdr, (unsigned char *)&hdr, 0,
> + vhost_hlen)) {
> + vq_err(vq, "Unable to write vnet_hdr at addr %p\n",
> + vq->iov->iov_base);
> break;
> }
> - len += hdr_size;
> - vhost_add_used_and_signal(&net->dev, vq, head, len);
> + /* TODO: Should check and handle checksum. */
> + if (vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF) &&
> + memcpy_toiovecend(vq->hdr, (unsigned char *)&headcount,
> + offsetof(typeof(hdr), num_buffers),
> + sizeof(hdr.num_buffers))) {
> + vq_err(vq, "Failed num_buffers write");
> + vhost_discard_desc(vq, headcount);
> + break;
> + }
> + len += vhost_hlen;
> + vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,
> + headcount);
> if (unlikely(vq_log))
> vhost_log_write(vq, vq_log, log, len);
> total_len += len;
> @@ -561,9 +599,21 @@ done:
>
> static int vhost_net_set_features(struct vhost_net *n, u64 features)
> {
> - size_t hdr_size = features & (1 << VHOST_NET_F_VIRTIO_NET_HDR) ?
> - sizeof(struct virtio_net_hdr) : 0;
> + size_t vhost_hlen, sock_hlen, hdr_len;
> int i;
> +
> + hdr_len = (features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ?
> + sizeof(struct virtio_net_hdr_mrg_rxbuf) :
> + sizeof(struct virtio_net_hdr);
> + if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) {
> + /* vhost provides vnet_hdr */
> + vhost_hlen = hdr_len;
> + sock_hlen = 0;
> + } else {
> + /* socket provides vnet_hdr */
> + vhost_hlen = 0;
> + sock_hlen = hdr_len;
> + }
> mutex_lock(&n->dev.mutex);
> if ((features & (1 << VHOST_F_LOG_ALL)) &&
> !vhost_log_access_ok(&n->dev)) {
> @@ -574,7 +624,8 @@ static int vhost_net_set_features(struct
> smp_wmb();
> for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
> mutex_lock(&n->vqs[i].mutex);
> - n->vqs[i].hdr_size = hdr_size;
> + n->vqs[i].vhost_hlen = vhost_hlen;
> + n->vqs[i].sock_hlen = sock_hlen;
> mutex_unlock(&n->vqs[i].mutex);
> }
> vhost_net_flush(n);
> diff -ruNp net-next-v0/drivers/vhost/vhost.c net-next-v7/drivers/vhost/vhost.c
> --- net-next-v0/drivers/vhost/vhost.c 2010-04-22 11:31:57.000000000 -0700
> +++ net-next-v7/drivers/vhost/vhost.c 2010-04-28 11:16:13.000000000 -0700
> @@ -114,7 +114,8 @@ static void vhost_vq_reset(struct vhost_
> vq->used_flags = 0;
> vq->log_used = false;
> vq->log_addr = -1ull;
> - vq->hdr_size = 0;
> + vq->vhost_hlen = 0;
> + vq->sock_hlen = 0;
> vq->private_data = NULL;
> vq->log_base = NULL;
> vq->error_ctx = NULL;
> @@ -861,6 +862,53 @@ static unsigned get_indirect(struct vhos
> return 0;
> }
>
> +/* This is a multi-buffer version of vhost_get_desc
> + * @vq - the relevant virtqueue
> + * datalen - data length we'll be reading
> + * @iovcount - returned count of io vectors we fill
> + * @log - vhost log
> + * @log_num - log offset
> + * returns number of buffer heads allocated, negative on error
> + */
> +int vhost_get_desc_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
> + int datalen, unsigned *iovcount, struct vhost_log *log,
> + unsigned int *log_num)
> +{
> + unsigned int out, in;
> + int seg = 0;
> + int headcount = 0;
> + int r;
> +
> + while (datalen > 0) {
> + if (headcount >= VHOST_NET_MAX_SG) {
> + r = -ENOBUFS;
> + goto err;
> + }
> + heads[headcount].id = vhost_get_desc(vq->dev, vq, vq->iov + seg,
> + ARRAY_SIZE(vq->iov) - seg, &out,
> + &in, log, log_num);
By the way, logging here looks broken to me.
Does live migration work for you?
log_num gets zeroed out on each call to vhost_get_desc.
I guess we could just change vhost_get_desc not to zero out
log_num at the start, do it here instead,
and pass in log + *log_num instead of log_num.
Need to also document the API for vhost_get_desc noting
that log_num is incremented, not stored to.
Pls think about it.
> + if (heads[headcount].id == vq->num) {
> + r = 0;
> + goto err;
> + }
> + if (out || in <= 0) {
> + vq_err(vq, "unexpected descriptor format for RX: "
> + "out %d, in %d\n", out, in);
> + r = -EINVAL;
> + goto err;
> + }
> + heads[headcount].len = iov_length(vq->iov + seg, in);
> + datalen -= heads[headcount].len;
> + ++headcount;
> + seg += in;
> + }
> + *iovcount = seg;
> + return headcount;
> +err:
> + vhost_discard_desc(vq, headcount);
> + return r;
> +}
> +
> /* This looks in the virtqueue and for the first available buffer, and converts
> * it to an iovec for convenient access. Since descriptors consist of some
> * number of output then some number of input descriptors, it's actually two
> @@ -868,7 +916,7 @@ static unsigned get_indirect(struct vhos
> *
> * This function returns the descriptor number found, or vq->num (which
> * is never a valid descriptor number) if none was found. */
> -unsigned vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
> +unsigned vhost_get_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
> struct iovec iov[], unsigned int iov_size,
> unsigned int *out_num, unsigned int *in_num,
> struct vhost_log *log, unsigned int *log_num)
> @@ -986,9 +1034,9 @@ unsigned vhost_get_vq_desc(struct vhost_
> }
>
> /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
> -void vhost_discard_vq_desc(struct vhost_virtqueue *vq)
> +void vhost_discard_desc(struct vhost_virtqueue *vq, int n)
> {
> - vq->last_avail_idx--;
> + vq->last_avail_idx -= n;
> }
>
> /* After we've used one of their buffers, we tell them about it. We'll then
> @@ -1033,6 +1081,68 @@ int vhost_add_used(struct vhost_virtqueu
> return 0;
> }
>
> +static void vhost_log_used(struct vhost_virtqueue *vq,
> + struct vring_used_elem __user *used)
> +{
> + /* Make sure data is seen before log. */
> + smp_wmb();
> + /* Log used ring entry write. */
> + log_write(vq->log_base,
> + vq->log_addr +
> + ((void __user *)used - (void __user *)vq->used),
> + sizeof *used);
> + /* Log used index update. */
> + log_write(vq->log_base,
> + vq->log_addr + offsetof(struct vring_used, idx),
> + sizeof vq->used->idx);
> + if (vq->log_ctx)
> + eventfd_signal(vq->log_ctx, 1);
> +}
> +
> +static int __vhost_add_used_n(struct vhost_virtqueue *vq,
> + struct vring_used_elem *heads,
> + unsigned count)
> +{
> + struct vring_used_elem __user *used;
> + int start;
> +
> + start = vq->last_used_idx % vq->num;
> + used = vq->used->ring + start;
> + if (copy_to_user(used, heads, count * sizeof *used)) {
> + vq_err(vq, "Failed to write used");
> + return -EFAULT;
> + }
> + /* Make sure buffer is written before we update index. */
> + smp_wmb();
> + if (put_user(vq->last_used_idx + count, &vq->used->idx)) {
> + vq_err(vq, "Failed to increment used idx");
> + return -EFAULT;
> + }
> + if (unlikely(vq->log_used))
> + vhost_log_used(vq, used);
> + vq->last_used_idx += count;
> + return 0;
> +}
> +
> +/* After we've used one of their buffers, we tell them about it. We'll then
> + * want to notify the guest, using eventfd. */
> +int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
> + unsigned count)
> +{
> + int start, n, r;
> +
> + start = vq->last_used_idx % vq->num;
> + n = vq->num - start;
> + if (n < count) {
> + r = __vhost_add_used_n(vq, heads, n);
> + if (r < 0)
> + return r;
> + heads += n;
> + count -= n;
> + }
> + return __vhost_add_used_n(vq, heads, count);
> +}
> +
> /* This actually signals the guest, using eventfd. */
> void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
> {
> @@ -1062,6 +1172,15 @@ void vhost_add_used_and_signal(struct vh
> vhost_signal(dev, vq);
> }
>
> +/* multi-buffer version of vhost_add_used_and_signal */
> +void vhost_add_used_and_signal_n(struct vhost_dev *dev,
> + struct vhost_virtqueue *vq,
> + struct vring_used_elem *heads, unsigned count)
> +{
> + vhost_add_used_n(vq, heads, count);
> + vhost_signal(dev, vq);
> +}
> +
> /* OK, now we need to know about added descriptors. */
> bool vhost_enable_notify(struct vhost_virtqueue *vq)
> {
> @@ -1086,7 +1205,7 @@ bool vhost_enable_notify(struct vhost_vi
> return false;
> }
>
> - return avail_idx != vq->last_avail_idx;
> + return avail_idx != vq->avail_idx;
> }
>
> /* We don't need to be notified again. */
> diff -ruNp net-next-v0/drivers/vhost/vhost.h net-next-v7/drivers/vhost/vhost.h
> --- net-next-v0/drivers/vhost/vhost.h 2010-04-24 21:37:41.000000000 -0700
> +++ net-next-v7/drivers/vhost/vhost.h 2010-04-26 10:35:25.000000000 -0700
> @@ -84,7 +84,9 @@ struct vhost_virtqueue {
> struct iovec indirect[VHOST_NET_MAX_SG];
> struct iovec iov[VHOST_NET_MAX_SG];
> struct iovec hdr[VHOST_NET_MAX_SG];
> - size_t hdr_size;
> + size_t vhost_hlen;
> + size_t sock_hlen;
> + struct vring_used_elem heads[VHOST_NET_MAX_SG];
> /* We use a kind of RCU to access private pointer.
> * All readers access it from workqueue, which makes it possible to
> * flush the workqueue instead of synchronize_rcu. Therefore readers do
> @@ -120,16 +122,23 @@ long vhost_dev_ioctl(struct vhost_dev *,
> int vhost_vq_access_ok(struct vhost_virtqueue *vq);
> int vhost_log_access_ok(struct vhost_dev *);
>
> -unsigned vhost_get_vq_desc(struct vhost_dev *, struct vhost_virtqueue *,
> +int vhost_get_desc_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
> + int datalen, unsigned int *iovcount, struct vhost_log *log,
> + unsigned int *log_num);
> +unsigned vhost_get_desc(struct vhost_dev *, struct vhost_virtqueue *,
> struct iovec iov[], unsigned int iov_count,
> unsigned int *out_num, unsigned int *in_num,
> struct vhost_log *log, unsigned int *log_num);
> -void vhost_discard_vq_desc(struct vhost_virtqueue *);
> +void vhost_discard_desc(struct vhost_virtqueue *, int);
>
> int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
> -void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
> +int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
> + unsigned count);
> void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
> - unsigned int head, int len);
> + unsigned int id, int len);
> +void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
> + struct vring_used_elem *heads, unsigned count);
> +void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
> void vhost_disable_notify(struct vhost_virtqueue *);
> bool vhost_enable_notify(struct vhost_virtqueue *);
>
> @@ -149,7 +158,8 @@ enum {
> VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) |
> (1 << VIRTIO_RING_F_INDIRECT_DESC) |
> (1 << VHOST_F_LOG_ALL) |
> - (1 << VHOST_NET_F_VIRTIO_NET_HDR),
> + (1 << VHOST_NET_F_VIRTIO_NET_HDR) |
> + (1 << VIRTIO_NET_F_MRG_RXBUF),
> };
>
> static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
>
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